Download The Nervous System

The Nervous System
• The nervous system has a coordinating role
where it receives, processes, stores, and
transmits information that comes from the
body and the outside world
Structure of a Neuron
•The neuron is the basic unit (cell) of nervous system
•Impulses are carried throughout the body by nerves.
dendrites are small extensions surrounding the cell body
which receive impulses (0.005 - 0.5mm long)
Axon Is the longest part of the neuron which propagates the impulse
Away from the cell body (0.5mm to 1m long)
The neurons are the only cells that
react to a
A stimulus is a change in the environment
that results in nerve excitation.
Example: sun shining in your eyes
or hearing a sound
• Nerves are structures that help transmit
information between the central nervous
system and the various regions of the body
• *
Neurotransmitter
released in synapse
Impulse transmitted
to next neuron
• Neurons must pick up stimuli, transform
them into nerve impulses and then transmit
these impulses on to the next neuron
• A nerve impulse is therefore any electric
signal transmitted by a neuron
• As signals move from one neuron to
another, they must cross the synapse. This
is the transition zone between two neurons
(a very small gap)
Basic Tasks of the Nervous
System
Sensory Input:
Monitor both
external and internal
environments.
Integration: Process
the information and
often integrate it with
stored information.
Motor output: If
necessary, signal
effector organs to
make an appropriate
response.
The Central Nervous System
The Central Nervous System is made of the
brain and the spinal cord.
The Brain
•The brain controls everything in the body.
•The brain contains more than 100 billion
neurons (nerve cells) and is the biggest
part of the central nervous system!
Parts of the Brain
The Brain has three main parts…
1. The Cerebrum
2. The Cerebellum
3. Medulla oblongata
(The Brain Stem)
The Cerebrum
•the largest part of the brain.
•It controls your:
1. thinking.
2. memory.
3. speaking.
4. Movement
5. Identifies information gathered by your
sense organs.
Lobes of the Brain
• The cerebrum is divided into several lobes, each
of which is responsible for different tasks
• The frontal lobes are responsible for problem
solving and judgment and motor function.
• The parietal lobes manage sensation, handwriting,
and body position.
• The temporal lobes are involved with memory and
hearing.
• The occipital lobes contain the brain's visual
processing system.
The Cerebellum
• below and to the back of the cerebrum.
•controls your balance and posture.
The Medulla Oblongata (Brain
Stem)
• connects the brain to the spinal
cord.
• controls your heartbeat,
breathing, and blood pressure.
•Responsible for certain reflexes : coughing,
swallowing, hiccups, vomiting and sneezing
Brain Stem
Grey Matter vs White Matter
• The brain can be divided into two types of
tissue: grey and white matter
• Grey matter:
– The part of the brain controlled by nerve cell
bodies and dendrites.
– It is grey in appearance and is where the true
processing occurs
– Makes up 40% of the human brain and requires
94% of available oxygen
• White Matter:
– Composed of axons
– Found in the center of the brain and between the
brain stem and cerebellum
– Facilitates communication between the grey matter
of the brain and between the brain and the rest of
the body
– Makes up 60%
of the human brain
The Spinal Cord
 connects the brain to the rest
of the nervous system.
 sends messages to and from
the brain.
•The spinal cord is protected by
small bones called vertebrae
Peripheral Nervous System
The Peripheral Nervous
System
Consists of all the nerves that leave the
spinal cord or brain reaching all parts of the
body.
 It has 2 types of nerves
 Sensory nerves – sending info to CNS
 Motor nerves – sending info to muscles
Voluntary Acts
 This system contains the skeletal
muscles
 Responsible for the conscious control of
our movement
 Signals from the brain effectuate
contractions of the muscles
Reflex
• is an involuntary automatic reaction
that happens without thinking about it.
• A reflex happens quickly
in less than a second.
The brain is not involved in a reflex.
Sensory Receptor
(responds to a stimulus by
producing a impulse)
Sensory Neuron
(axon conducts impulse)
Integrating Center
(Relay impulse from
sensory to motor neurons)
Motor Neuron
(axon conducts impulse
to effector)
Effector
(muscle that responds to
A motor nerve impulse)